We Are Together, But We Keep It A Secret

Before I share my problem with you, I will just say that I did not want it to happen at all. People said "if you have a dream, follow it" and "if something makes you happy, then nothing else matters" yes, but not! I'm with the person I'm really happy with right now, but what of it when I can't shout it to the whole world, and everything has to be a secret. And I am to blame for everything! Here is my story ... It all started a long time ago. When I met him, he was even disliked by me. Over time, however, I began to get to know him, and he turned out to be an amazing person and friend. Maybe that's why I started to sympathize with him, and gradually they grew stronger and stronger. Perhaps this was my biggest mistake in allowing this to happen. And here's why ... He was my best friend's boyfriend. They themselves hid from the others that they were together and only I knew about it. That's why I always participated in my girlfriend's plans to pretend to be a boyfriend with him in front of others. At first it was all a joke. Yes, but over time I began to feel feelings for this man, and as much as it seemed to me, I tried to suppress them. It was the same with him, even though he was really in love with my girlfriend. Neither I nor he acknowledged our feelings for each other. On top of that, we constantly wrote to each other and heard each other. I couldn't help but do it. It was ruining me from the inside to watch them together, to hear about him all the time, but somehow I remained strong. In time, however, things went wrong between them. I don't know if it's because of him or her. She started dating others even though she was still with him. Finally he told her that he can't and doesn't want to be with her anymore and they broke up. They haven't been together for a long time. She has a new person next to her who really loves her, and he loves her. She tells me that he is no longer interested in her and does not want to be with him, but she will always remain a weakness. They remained friends even if they were rarely heard, which is really nice. However, things can no longer be hidden between him and me, and we got together some time ago. Now he tells me that he wants to tell everyone that we are together and that no one has made him feel this way before and that he loves me painfully. Although I really want everything to come to light, I'm afraid that she will understand and hate me, and to be honest, she's right. As much as I want to forget it, I can't. I keep dreaming about him, I think about him all the time, and when we're together I feel that I fly to heaven. Now that we are together, I feel that he is the person I was looking for. Please tell me how to proceed. I can't consult anyone. Do you think that I should follow my happiness and tell everyone that we are together and especially on it, or should we separate because we act like the greatest traitors and do not deserve to be together?